Figure 2.

Using the permanent magnet-based magnetic tweezers to measure the force changes of DNA origami structures. (a) A complicated system combined with high-resolution magnetic tweezers and dual-color single-molecule fluorescence detection. Magnifying cartoon showed the DNA sample, consisting of a 40 bp hairpin that is flanked by a 5.9 kb double-stranded DNA spacer. Donor and acceptor fluorophores for FRET detection are shown in green and red, respectively. Concretely, at high force, the hairpin opens, while it is closed at low forces. Reprinted with permission from Ref. [30]. Copyright 2016 American Chemical Society. (b) Linear fits the data (solid black lines) provide torsional persistence lengths of 530 ± 20 nm and 390 ± 30 nm for the 6HB (d) and 4HB (e), respectively. 2.0 pN (red circles) and 3.7 pN (red triangles) referred to the 6HB; 9 pN (green circles) and 6 pN (green triangles) referred to the 4HB. Reprinted with permission from Ref. [28]. Copyright 2011 American Chemical Society.